1. Technical Field
The present disclosure generally relates to heating devices, and more particularly, to a heating module for integrating into an electrical appliance, for example in a household appliance such as a coffee machine, or in a laboratory apparatus.
2. Description of the Related Art
Heating modules are used as heat sources in household appliances such as coffee machines or laboratory apparatuses.
In some devices from the state of the art, e.g., in DE 25 37 769 A1, a heating coil is used in order to use the heating surface to heat a cover plate with a heating function.
However, it is detrimental in the case of the device of DE 25 37 769 A1, that the heating coil requires additional power control by means of a protective thermostat, in order to prevent the heating coil from overheating. This results in increased manufacturing costs for the electrical appliance in which the heating module of DE 25 37 769 A1 is used, while simultaneously increasing its susceptibility to failure.
It is possible to do without a power control if a PTC element (Positive Temperature Coefficient) is used as the heat source of the heating module, as is the case, for example, in the heating modules of DE 28 04 818 C2 and DE 29 48 591 C2. By its material properties, the PTC element heats up only until a predefined temperature limit is reached; above the temperature limit the PTC element automatically switches off the heat production. This advantage of the PTC element is offset, however, by the fact that its attachment in the heating module requires a complex design and can be implemented only with high manufacturing expenditures. Consequently, in the heating modules of DE 28 04 818 C2 and DE 29 48 591 C2, additional mechanisms in the form of clamps and springs are provided, by means of which the PTC heating element is held against a heating body in order to achieve good heat transfer.
In order to avoid this, another way is chosen in EP 0 573 691 B1. A PTC element is pressed in an extruded shape having a heatable base plate as a heating surface. Detrimental in the heating module of EP 0 573 691 B1, however, is that, because of its restricted functionality, use in the area of household appliances and laboratory apparatuses remains restricted as compared to the devices of DE 28 04 818 C2 and DE 29 48 591 C2.
In DE 200 20 347 U1, a liquid heating tube is described in which a PTC heating element is placed in a hollow space of a heating body. In a flow hole also formed in the heating body, longitudinal ribs are arranged for good heat transfer to a liquid that flows through the flow hole, which also may result in complicated and/or expensive manufacturing.
U.S. Pat. No. 5,724,478 discloses a heating assembly with several flow conduits, in which water flowing through can be heated.